ELECTRON MICROSCOPE STUDIES ON THE MORPHOLOGICAL CHANGES IN RABBIT PLATELETS INDUCED BY ADENOSINE DIPHOSPHATE (ADP), METABOLIC INHIBITORS OR INHIBITORS OR PLATELET AGGREGATION

The shape changes in rabbit platelets induced by ADP, NEM, KCN, PGE, , aspirin or distilled water were investigated using Born's method and electron microscopy. The following results were obtained : 1) The optical density of EDTA-PRP was increased rapidly after the addition of ADP, NEM or distilled water. ADP-induced increase in optical density has been thought to be resulted from the shape change of platelets. It could be confirmed by electron microscopy that the change in optical density was due to the morphological change in platelets.2) When ADP was added to PRP, platelets changed their shape from “disc” to “spiny sphere” with a marked pseudopodia formation. Both microtubules and granules were concentrated in the center of platelet. This type of morphological change was followed by the platelet aggregation.3) The platelets treated with NEM became also spherical and posessed several number of pseudopodia. As compared to ADP-induced changes, however, the pseudopodia were much shorter, microtubules were destroyed and granules were not concentrated. This kind of morphological change was not followed by the platelet aggregation. The same kind of change was introduced by the addition of distilled water.4) The optical density of PRP was also increased by addition of KCN and PGE1, but no significant change in platelet morphology was found by electron microscopy.5) Aspirin also induced no changes in the shape of platelets.6) From these results, the relationship between platelet shape change and aggregation of platelets was discussed, and it was suggested that the contractile proteins in the platelets might play an important role in such a shape change as well as the aggregation of platelets.